Hi Everyone,
This a relatively old post but I see that people (including myself) who are setting up their SCCM infrastructure are asking the same question about setting a ComputerName during the OSD task sequence.
I originally gave the steps a try but it was not working for me in the beginning.
Through another info source on SCCM, I learned that when deploying your OSD TS to All Unknown Computers, you MUST set the deployment type to AVAILABLE and not required. Once I re-deployed to a test PC, voila!! everything started to work as described in the original post.
I'm pretty sure that this important step is not mentioned anywhere in this topic thread so I figured I would add it in case anyone else out there is getting stuck on this too.